March 18, 2026
Speakers at Upstream 2026
Upstream 2026 has a great range of speakers. Here is a little overview for you
Melissa Ablett-Jordaan, Founder Sibyl
She will be our Moderator on the Main stage.
Melissa Ablett-Jordaan is an event host, moderator, and growth-focused executive working at the intersection of innovation, entrepreneurship, and women’s health. She is the founder of Sibyl, an AI-native platform focused on reproductive mental health, starting with pregnancy loss.
Previously, Melissa served as Chief Operating Officer of CIC, leading startup hubs across eight cities worldwide, and has worked in U.S. innovation policy and early-stage media startups. She lives in Rotterdam with her husband, two children, and her miniature dachshund.
Matthijs Welle is the CEO of Mews, a hospitality technology platform transforming how hotels operate and serve guests. Today, Mews supports hotels and hospitality businesses in 85 countries, with 12,500 customers live on the platform. Prior to Mews, Matthijs spent nearly a decade at Hilton, building deep expertise in hotel operations and commercial strategy. He studied hotel management and has lived and worked abroad for over 20 years in highly international environments.
Arosha Brouwer, Chief Impact Officer TrueTribe
Arosha Brouwer is Chief Impact Officer at TrueTribe. She founded and led Quan, a Y Combinator–backed company that raised over €3M and partnered with global enterprises, before its acquisition by TrueTribe. Arosha focuses on translating research, data, and innovation into practical solutions that improve how people and organisations work.
TrueTribe is a data-driven wellbeing platform that helps organisations prevent absenteeism and strengthen sustainable performance. It brings together risk prediction, employee assistance, organisational insights, and provider management in one system – enabling earlier intervention, targeted support, and better decisions about people, leadership, and work culture.
Siete Hamminga, CEO and founder Robin Radar Systems
Siete Hamminga is the CEO and founder of Robin Radar Systems, a Technology Leader in radars for short range, small targets like birds and drones. He has a Master in Science degree from the University of Twente and finished his studies in Silicon Valley. He then founded several high tech companies, before spinning out TNO radar technology into a commercial venture in 2010, Robin Radar.
Under his leadership, Robin Radar pivoted from preventing bird strikes at airports like Schiphol to protecting against drones in defense & security. As winner of several prestigious awards for entrepreneurship, Hamminga has grown the firm to 250+ staff and €100M+ turnover. He authored Beyond the Hype and also serves on boards for NIVD and TNO.
Thijn van Helvoirt, VC Partner & Investor No Such Ventures
Thijn van Helvoirt is a tech founder turned VC Partner at No Such Ventures, investing in Europe’s most promising software-first startups with flexible capital and relentless support.
He previously co-founded and scaled the mobility tech company Check from idea to a profitable multinational with 250+ employees, raising €15m in equity. With experience across venture capital, M&A, and capital markets, he now backs founders building the next generation of European market leaders.
See them all at Upstream 2026!